To be quite honest, it isn't difficult and that is why the oil
companies are so worried. because with a few simple ingredients, that
you already use when cleaning windows or camping, you can convert
rapeseed oil to diesel for your car.
You can make it in your own garage and drive for a fraction of the cost
of fossil diesel.
And that is not all...
Biodiesel is actually cleaner than normal petro diesel, it does not add
any carbon dioxide to the environment, because the plants used to make
the raw oil consume carbon dioxide while they grow. Reduce greenhouse
gasses in one go!
http://biodieseloxea.blogspot.com/